[Oakland Rob]

From just looking at the lenses how does one determine if it requires setting the camera in M mode, vs being able to use Av (or P)?

My SMC Pentax M 35mm f2.8 lens and SMC Pentax 28mm f3.5 only work in M. But my smc Pentax M 200mm F4 works in P/Av.

I can keep it straight by marking those, but now I'm curious about why some only work in M but not Av. None have the auto-aperture setting.

[othar]

But my smc Pentax M 200mm F4 works in P/Av.

I think you should check that again, when set to P or Av with a lens without the A-setting on the aperture ring (or when the aperture ring is set to somewhere else) the camera will still take pictures in a semi Av mode (with all the lenses you mentioned), but it will only use the lenses wide open

[Oakland Rob]

Doh! You're right. I must have left it in M. You can hear it stop down when the green button is pushed, so the absence of that should have alerted me that it was working the same as the others.

So sorry...my bad. Never mind,

[Adam]

From just looking at the lenses how does one determine if it requires setting the camera in M mode, vs being able to use Av (or P)?

My SMC Pentax M 35mm f2.8 lens and SMC Pentax 28mm f3.5 only work in M. But my smc Pentax M 200mm F4 works in P/Av.

I can keep it straight by marking those, but now I'm curious about why some only work in M but not Av. None have the auto-aperture setting.

Here are some resources, though as already noted, things will generally be consistent across an entire lens series:
The Pentax K-mount Camera Lens Compatibility Chart

Check Lens Compatibility with Your Pentax Camera

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers: